Field of the Invention
The present disclosure relates to an organic light emitting display device, and more particularly, to an organic light emitting display device and a method for manufacturing the organic light emitting display device which is improved in light efficiency and also capable of compensating a viewing angle by including a light scattering layer formed by using a photosensitive resin composition which can be photo-patterned.
Description of the Related Art
An organic light emitting display device is a self-light emitting display that does not need a separate light source unlike a liquid crystal display device. Thus, the organic light emitting display device can be manufactured into a lightweight and thin form factor. Further, the organic light emitting display device is advantageous in terms of power consumption since it is driven with a low voltage. Also, the organic light emitting display device has excellent color expression ability, a high response speed, a wide viewing angle, and a high contrast ratio (CR). Therefore, the organic light emitting display device has been considered as a next-generation display device.
A bottom-emission organic light emitting display device refers to an organic light emitting display device in which light emitted from an organic light emitting element is released to a bottom side of the organic light emitting display device. It also means an organic light emitting display device in which the light emitted from an organic light emitting element is released in a direction toward a bottom surface of a substrate on which a thin film transistor for driving the organic light emitting display device is formed. The light emitted from an organic light emitting layer of a bottom-emission organic light emitting display device can be roughly classified into an ITO/organic mode (hereinafter, referred to as “ITO mode”), a substrate mode, and an air mode on the basis of a light propagation path. The air mode refers to the light extracted to the outside of the organic light emitting display device, among lights emitted from the organic light emitting layer; the substrate mode refers to the light confined within the organic light emitting display device due to total reflection on the substrate among lights emitted from the organic light emitting layer; and the ITO mode refers to the light confined within the organic light emitting display device due to total reflection on an anode, generally formed of ITO, among lights emitted from the organic light emitting layer. In the bottom-emission organic light emitting display device, light confined within the organic light emitting display device as the ITO mode account for about 50% of the total light emitted from the organic light emitting layer. Further, light confined within the organic light emitting display device as the substrate mode account for about 30% of the total light emitted from the organic light emitting layer. Thus, the light accounting for about 80% of the total light emitted from the organic light emitting layer is confined within the organic light emitting display device and only light accounting for about 20% are extracted to the outside. Therefore, the improvement in light extraction efficiency of an organic light emitting display device is desirable.
Further, in a top-emission organic light emitting display device in which light emitted from an organic light emitting element is released to a top side of the organic light emitting display device, i.e., the opposite side to a substrate on which a thin film transistor for driving the organic light emitting display device is formed. As a result, a considerable amount of light is lost in a waveguide mode and a surface plasmon mode. To be specific, in the waveguide mode, some of light emitted from the organic light emitting element may be total-reflected within the organic light emitting display device due to a difference in refractive index between various components within the organic light emitting display device and then confined within the organic light emitting display device. Further, in the plasmon mode, some of light emitted from the organic light emitting element may be lost in the form of surface plasmon due to a surface plasmon phenomenon occurring adjacent to a metal electrode constituting the organic light emitting element. As described above, the light accounting for about 50% or more of the total light emitted from the organic light emitting element are lost in the waveguide mode and the surface plasmon mode.
Therefore, the improvement in light extraction efficiency of both of a top-emission organic light emitting display device and a bottom-emission organic light emitting display device is desirable.
A technique using a light extraction component including particles capable of scattering light has been used in order to improve light extraction efficiency. To be specific, a technique of forming the light extraction component on the front surface of a substrate has been used. However, if the light extraction component is formed on the front surface of the substrate, the light emitted from a light emitting region of a specific pixel may be extracted to the outside of the substrate through the light extraction component positioned in a region other than the light emitting region, which may cause a blurring phenomenon. Accordingly, a method for forming a light extraction component by patterning may be considered. However, a light extraction component of the related art is formed of a material which cannot be photo-patterned. Thus, an etching process for patterning the light extraction component is needed. However, during the etching process, other elements around the light extraction component may be damaged. Thus, realistically, the light extraction component cannot be patterned using techniques available thus far.
Meanwhile, the research on an organic light emitting display device employing a micro cavity structure to improve the light efficiency of the organic light emitting display device has been in progress. A micro cavity means that light is repeatedly reflected between two layers spaced from each other by an optical length, and, thus, the light having a specific wavelength is amplified through constructive interference. In a top-emission organic light emitting display device, a micro cavity is applied such that the light emitted from an organic light emitting layer is repeatedly reflected between an anode including a reflective layer and a cathode formed into a semi-transmissive layer. Further, in a bottom-emission organic light emitting display device, a micro cavity is weaker in intensity than the micro cavity of the top-emission organic light emitting display device, but can be applied for a process in which light emitted from an organic light emitting layer is reflected from a cathode.
In an organic light emitting display device employing a micro cavity as described above, a front luminance is increased. Therefore, light efficiency of the organic light emitting display device is improved, and, thus, power consumption and a life of the organic light emitting display device can also be improved. However, in the organic light emitting display device, a front view characteristic and a viewing angle characteristic are in inverse proportion to each other. Thus, an increase in front luminance results in a decrease in lateral luminance. Further, in the organic light emitting display device employing a micro cavity, the light frontally emitted from a sub-pixel is different in optical length from the light laterally emitted from the same sub-pixel. Therefore, a color shift phenomenon depending on a viewing angle may occur. Accordingly, there has been a demand for suppressing variations in luminance and color coordinate depending on a viewing angle in the organic light emitting display device employing a micro cavity.